In the process for the preparation of a semiconductor device, for example, a resist material is applied to a wafer such as silicon. The resist material is then subjected to ordinary photographic process to form an image made of resist pattern. With this image as a mask, the wafer is then etched. Unnecessary resist material is then removed. This procedure is then repeated. Unnecessary resist material is removed also in the case where a circuit is formed on various circuit boards.
With the recent tendency towards the enhancement of the density and integration of LSI and the density and size of liquid crystal panel, it has been important more and more from the standpoint of yield and reliability of product to simply and certainly remove unnecessary resist material from semiconductor wafer or glass substrate. Heretofore, a dry removal process using an asher (carbonization apparatus) or a wet removal process using a resist removing solvent has been normally employed at the step of removing unnecessary resist material.
However, the removal process using an asher is disadvantageous in that it takes much time to remove a resist material which has been doped with ions at a high dose. If plasma ashing is effected, the semiconductor substrate can be damaged by plasma. The wet removal process using a resist removing solvent is disadvantageous in that it deteriorates the working atmosphere and discharges waste liquid that pollutes the global atmosphere. This wet removal process is also disadvantageous in that the resist material which has once been removed could be again attached to the wafer.
In order to solve these problems, a process for the removal of a resist material has been proposed involving the use of a sheet-like or tape-like pressure-sensitive adhesive sheet. This removal process comprises applying a pressure-sensitive adhesive sheet to an object having a resist material provided thereon so that the resist material is fixed to the pressure-sensitive adhesive layer, and then peeling the pressure-sensitive adhesive sheet off the object together with the resist material to remove the resist material from the object. This removal process is free from the problems inherent to the conventional removal processes using an asher or solvent, contributing to the enhancement of the yield of product.
However, the foregoing removal process using a pressure-sensitive adhesive sheet is disadvantageous in that, in cases where some kinds of resist material are used or some kinds of treatment on resist material are effected, the resist material can not be removed completely from an object such as semiconductor substrate. In particular, resist materials doped with ions at a dose as high as not less than 1.times.10.sup.15 ions/cm.sup.2 can be hardly peeled off the substrate in most cases.